1. Field of the Invention
The present invention relates to a control apparatus and method for an autonomous traveling vehicle and more specifically to a control apparatus having a teaching mode in which the vehicle travels while its own position and direction at a plurality of points on a running path are memorized and a playback mode in which the vehicle travels while the running path memorized in the teaching mode is played back.
2. Prior Art
In recent y ears, computer controlled, self guiding, 16 unmanned operated, autonomously traveling vehicles have been developed for cutting grasses, mowing lawn or doing other works in fields such as golf courses, banks of rivers, parks and the like. Many of such autonomous vehicles, since they repeat the same works in the same areas in most cases, introduce so-called teaching-and-playing back control method in which the vehicle travels autonomously by playing back the running path which have been memorized beforehand.
For example, Japanese Patent Application Laid-open No. Toku-Kai-Sho 59-105112 discloses a technique in which a distance between a next target point and a previous target point, a reference azimuth which is an angle of the running direction with respect to the direction of earth magnetism and a running azimuth which is an angle of the running direction with respect to the direction of the next target point, have been taught beforehand and when the vehicle runs in the play-back mode, these data are read out. The vehicle runs while correcting a discrepancy produced between these data and the present position.
Further, Japanese Patent Application Laid-open No. Toku-Kai-Hei 3-135606 discloses a technique in which a reference azimuth of a working vehicle is established by a teaching including a manual operation of the vehicle.
However, since sensors for detecting the vehicle position have measuring errors, the data containing the measuring errors of the sensor are memorized at teaching.
Hence, an attempt to play-back a running path with fidelity by minimizing the deviation between the vehicle position detected by the sensors and the vehicle position acquired by teaching produces an increased steering gain and as a result the measuring errors of the sensors generates fluctuations in the steering system as shown in FIG. 11.
The present invention is intended to obviate the aforesaid problem of the prior arts and it is an object of the present invention to provide a control apparatus of an autonomous traveling vehicle capable of playing back a running path acquired by teaching with an excellent steering stability without increasing tracing errors due to the measuring errors of the sensors.
To achieve the object, the present invention comprises a virtual traction point establishing means for establishing a virtual traction point located away from a vehicle position by a specified distance in a direction of a vehicle azimuth, a current vehicle position determining means for determining a current vehicle position corresponding to the vehicle position in a play-back mode, a target azimuth calculating means for calculating a target azimuth based on a positional relationship between the current vehicle position and the virtual traction point, a vehicle steering means for steering the vehicle in a direction of the target azimuth in the play-back mode and a vehicle speed control means for controlling a vehicle speed such that a distance between the virtual traction point and the vehicle comes within a specified range in the play-back mode.